Belt speeds for sharpening

Just wondering what people think is the optimum speed for a sanding belt if it is used for sharpening.



I have an old Hafco disc/belt sander which is a bloody good unit. I calculated the belt speed at just over 3,000 feet per minute.



My bench grinder runs at 6,000 feet per minute.



I have researched as much as I can and found that some belt sharpening machines run at only 900 feet per minute.





Now speed equals heat, so is 3,00 feet per minute too fast??